This invention relates to a fire-resistant cellulosic insulation. Fire retardancy is achieved by the addition of a mixture of bauxite, dolomite, and boric acid to the cellulose insulation.
Finding effective, efficient, and safe insulating materials is one of the major problems of the building industry today. Faced with escalating energy costs and increasing costs of construction, the necessity for an effective insulation material which is inexpensive to manufacture and apply has become obvious. In addition, regulations relating to both the safety and flammability of building products have become far more stringent, and will contine to be more restrictive as the public becomes increasingly aware of the hazards inherent in presently utilized insulation materials. For example, asbestos and fiber glass have been identified as possible carcinogenic agents, and face potential abandonment by the construction industry. On the other hand, such insulation materials as cellulose fiber and shredded newspaper, while providing highly efficient sound and heat insulation, have been largely unacceptable due to flammability.
The applicable Federal Government Services Administration Specification, HH-I-515D, requires cellulose insulation to achieve a critical radiant flux of greater than 0.12 watts/cm.sup.2. Critical radiant flux, a measure of flame spread, is measured under controlled conditions, in accordance with the Specification, by placing a given amount of insulation loosely in a specimen tray, which is then placed in a chamber at a 30.degree. angle to an air-gas fueled radiant heat energy panel. A flame is applied to the specimen by a propane burner for five minutes, after which flame spread is measured, and the distance converted to watts/cm.sup.2 critical radiant heat flux by comparison to a standardized flux profile curve.
In addition, it is known that a major cause of fires in houses with cellulose insulation is from smoldering. Accordingly, a specification for smoldering has been incorporated in HH-I-515D, as determined by the "smolder box" test. In this standardized test, the insulation and fire retardant are placed in a metal box 20 cm square and 10 cm deep, said box resting on a glass fiberboard pad. A lighted unfiltered cigarette, 85.+-.2 mm long, with a packing density of 0.270.+-.0.020 g/cm.sup.3 and a total weight of 1.1 .+-.0.1 gm, is then placed upright in the middle of the insulation, and allowed to smolder for two hours. To pass the test, the weight loss of the insulation material may not exceed 15%, and the smoldering must be confined to less than 5 cm from the walls of the container.
In addition to the GSA Specification for cellulose insulation set forth by HH-I-515D, there are approximately twenty additional tests required for Underwriters Laboratory (UL) approval.
An ideal fire retardant composition for cellulosic insulation should be odorless, and it must not be hygroscopic, poisonous, or corrosive; it should retain its effectiveness permanently, and must adhere to the basic insulation material so firmly as to prevent its removal during ordinary usage, e.g. bending, folding, or loose fill application; it should not only prevent burning when exposed to flame or glowing, but should act to extinguish burning or smoldering; and it should do so without the release of any by-products or products of combustion which are poisonous, corrosive, or otherwise injurious.
The market for cellulose insulation is large, with 1977 cellulose insulation production estimated by the Department of Commerce at about 835,000 tons. There is general agreement that this market should expand for some time, until the retrofit market is saturated, and then decline to meet the requirements of the construction industry for new buildings. Accordingly, there has been considerable interest in developing a safe, effective, and inexpensive fire retardant additive for cellulose insulation.